Insertion devices for surgical instruments are known in the art. Prior art insertion devices of this general type have been quite complicated, cumbersome and difficult to use. Such devices have a relatively large diameter, a limited maximum length, a limited transmission of torque and present obstacles to insertion of instruments. For example, a disadvantage of such variably flexing insertion devices is that the device twists when applying torque to the proximal end and therefore the torque is not transmitted along the device toward the distal end. This makes it difficult or impossible to impart a circumferential movement along the device when needed to traverse the body.
In addition, prior art devices of this general type cannot be connected to an instrument, such as an endoscope or a colonoscope, in such a manner as to be reliable and sufficiently torque-transmitting, while at the same time being easily releasable therefrom and variably flexible. The operator of the device must have the ability to manipulate the instrument when necessary with the insertion device and yet free the instrument easily when necessary.